Wearable exoskeletons have been designed for medical, commercial, and military applications. Medical exoskeletons are generally designed to help restore a patient's mobility. Commercial and military exoskeletons are generally used to reduce loads supported by workers or soldiers during strenuous activities, thereby preventing injuries and augmenting the stamina, comfort, and/or strength of these workers or soldiers while engaged in strenuous activities.
The fatigue and stress on a person's body resulting from doing work that requires the person's arm to reach or hold a static posture are documented in occupational medicine. Holding a static posture places very high static loads on the body, resulting in rapid fatigue. Static postures add to the muscular effort required to do tasks and the lack of motion impedes blood flow. Similarly, the overuse of muscles and tendons in the upper body, including but not limited to the hands, arms, shoulders, back, and neck, can result in fatigue and repetitive strain injuries (RSIs). RSIs affect the musculoskeletal and nervous systems. Accordingly, there is a need in the art for an exoskeleton device that can reduce or prevent the fatigue and stress caused by such activities, thereby augmenting a wearer's performance and preventing injuries. In particular, there exists a need for an exoskeleton that assists a wearer by directly supporting the weight of the wearer's arm or arms and various tools held by the wearer, increasing the strength and stamina of the wearer during the performance of tasks. There further exists a need to enable a wearer to use tools in ways and for durations of time that would not be possible without an exoskeleton.
As exoskeleton devices become more prevalent, there further exists a need for an exoskeleton device that allows the wearer to use the exoskeleton device without the exoskeleton causing discomfort due to forces applied to the arms of the wearer. Imparting forces of any magnitude into the wearer's body should be done carefully. This can be accomplished in powered exoskeleton systems with software by providing safety limits. However, for a purely mechanical system, this must be accomplished through other means. One method known to those skilled in the art is to simply increase the surface area of the force applied and/or to heavily pad the force-applying surface. Yet, these solutions can be problematic as they prevent heat from being dissipated from the body and can obstruct range of motion. The issue of poor heat dissipation is a particular problem for wearers engaged in prolonged work activities, which is a major application area of assistive exoskeletons. In some cases, an exoskeleton wearer may experience extended exposure to the applied forces, such as during overhead work. The issue with functional range obstruction is another problem encountered by workers engaged in dynamic activities since, if obstructed, they may perform a compensatory motion to achieve the desired task, diverting strain to a new part of the body. There then further exists a need for an exoskeleton device to allow sufficient blood flow to the extremities, particularly the arms and hands of the wearer. Independent of use case, long-term exposure to forces of any magnitude can result in discomfort for the wearer, thus justifying a further need to allow users to wear the device comfortably.